The invention relates to an optical configuration for scanning a beam in two, fundamentally perpendicular axes, particularly for use in confocal laser scanning microscopes, with two mirrors that can be rotated, each by a drive, around two axes that lie perpendicular to each other (x-axis, y-axis).
Basically what is involved here is a configuration for scanning a beam in two, fundamentally perpendicular axes, the significant feature in the present case being the rotation of the light beam in both axes around the pupil of the lens or a plane conjugated to the lens.
Technical practice is already acquainted with highly differing embodiments of an x-y scanner. Different scanners are known from the paper by J. Montagu: "Two-axis beam steering system, TABS", Proceedings Reprint, SPIE--The International Society for Optical Engineering, Vol. 1920, 1993, pages 162-173 (reprinted from Smart Structures and Materials 1993: "Active and Adaptive Optical Components and Systems II", 1-4 February 1993, Albuquerque, N. Mex.).
With the single mirror scanner, a single mirror is provided that rotates around an axis; the rotating axis of the mirror does not correspond to the optical axis. Single mirror scanners generally comprise a gimbal-mounted mirror for scanning in both the x and y directions.
Here, to be sure, the single mirror minimizes the loss of light that occurs when there is a plurality of mirrors; on the other hand, the x galvanometer must be continuously kept in motion, i.e., its mass must be accelerated and braked. This limits the image rate to about 10 images per second, specifically because of the otherwise excessive vibrational inputs into the microscope system. Furthermore, a resonant scanner cannot be employed due to its required installation.
In a two-mirror scanner, two mirrors positioned at a predetermined angle are provided that normally turn around rotating axes that are orthogonally positioned. This kind of arrangement is not absolutely necessary, however. The incident beam in any case runs parallel to the rotating axis of the last mirror in the beam path.
Furthermore, so-called "paddle" scanners and "golf club" scanners, as special embodiments of the two-mirror scanner, are known to the prior art. In these scanners, rotation of the beam around a virtual pivot point is achieved only approximately, which basically results in imaging errors.
According to A. F. Slomba: "A laser flying spot scanner for use in automated fluorescence antibody instrumentation", Vol. 6, No. 3, May-June 1972, pages 230-234, mirror scanners are also known for use in fluorescence microscopy and in confocal microscopy. Reference is made thereto merely for supplementary purposes.
The known optical configurations discussed above for scanning a beam in two perpendicular axes are problematic in actual practice, and for a number reasons. Foremost among these reasons is certainly the large number of imaging errors, as well as the far-reaching problems associated with the fact that at least one of the drives must be continuously entrained, which results in a very considerable reduction in the image rate. In any case, the known two-mirror designs only approximately allow the beam to be rotated around a virtual pivot point, and a large number of imaging errors consequently arise in these scanners.